1. Field Of The Invention
The present invention relates to the field of turbomachine turbines, and more particularly for those that are to be found in gas turbines.
The present invention relates more precisely to a turbomachine having a positioning member for positioning a ring segment for a turbine wheel that is mounted to rotate about an axis inside a casing.
2. Description Of The Related Art
Traditionally, the wheels of turbomachine turbines, such as the high pressure turbines of helicopter gas turbines, are surrounded by a ring that is concentric about the turbine wheel. As a component element of the stator of the turbomachine, the ring forms an outer shroud for the turbine stage. In other words, the burnt gas leaving the combustion chamber flows between the hub of the turbine wheel and the ring in such a manner as to drive the turbine wheel in rotation.
Generally, the ring is constituted by a plurality of ring segments, also referred to as ring sectors, that are placed contiguously one after another.
These ring segments are generally not fastened securely to the turbomachine casing since they are liable to expand axially and radially as a result of the high temperatures conveyed by the burnt gas.
The ring segments are held inside the casing by one or more positioning members.
Furthermore, it is common practice to provide for cooling the ring segments by causing a cooling fluid to flow around the ring, the cooling fluid possibly being bled from the compressed air that is generated by the turbomachine compressor.
Nevertheless, such a configuration presents the drawback of creating leakage zones, and it can readily be understood that the burnt gas might penetrate into the cooling circuit or, conversely, that the cooling fluid might penetrate into the gas flow section located upstream or downstream from the turbine wheel, which would penalize the efficiency of the turbomachine, with the penalty being worse when ejection takes place downstream.
To avoid leaks, document U.S. Pat. No. 5,988,975 proposes a solution that consists in providing radial sealing by means of a ring that keeps the ring segments pressed radially against the casing.